In vitro fit of CAD-CAM complete arch screw-retained titanium and zirconia implant prostheses fabricated on 4 implants.

STATEMENT OF PROBLEM

Computer-aided designed and computer-aided manufactured (CAD-CAM) titanium and zirconia implant-supported fixed implant prostheses on 4 implants have become popular. The precision and accuracy of their interface fit has not been widely researched.

PURPOSE

The purpose of this in vitro study was to compare the marginal fit of zirconia and titanium implant-supported screw-retained CAD-CAM complete fixed dental prostheses (CFDP) fit with a standardized cast simulating the all-on-4 implant distribution.

MATERIAL AND METHODS

Representation of an edentulous maxilla with 4 multiunit replicas embedded in sites corresponding to the positions of the maxillary first molars and canines was chosen. Multiunit abutments were digitally scanned using scan bodies and a laboratory scanner. CAD software was used to design screw-retained implant-fixed complete prostheses framework, and the file was sent to a milling machine for CAM. Titanium (n=5) and zirconia (n=5) frameworks were milled on 4 implants, and the frameworks were scanned with an industrial computed tomography (CT) scanner while applying the 1-screw test. The direct CT scans were reconstructed to generate a standard tessellation language (STL) file from the voxel data set and transported to volume graphics analysis software from which measurements were extracted. The circular mating surfaces of the corresponding framework interfaces to their representative multiunit abutment replicas on the standard were measured for implant position left maxillary canine (LMC), implant position right maxillary canine (RMC) and implant position right maxillary first molar (RMFM). In addition, color maps were generated to show the marginal discrepancy between the mating surfaces using ±0.500 mm color scale ranges.

RESULTS

The material type (zirconia or titanium) was not significant for 3D discrepancy measurements (P=.904). However, 3D discrepancy measurement values were significantly different between RMC and RMFM within each group (P<.001). The mean 3D ±SD discrepancy measurement for LMC for titanium was 48.2 ±2.6 μm. The mean ±3D discrepancy measurement for RMC for titanium was 74 ±15 μm and 84.4 ±12.1 μm for zirconia. The mean 3D discrepancy measurement for RMFM for titanium was 102 ±26.7 μm and 93.8 ±30 μm for zirconia. All 3D discrepancy measurements showed values <135 μm.

CONCLUSIONS

Within the limitations of the present in vitro study, implant-supported CAD-CAM fabricated titanium and zirconia complete fixed dental prosthesis frameworks showed comparable marginal fit. Three-dimensional microgap measurements of frameworks showed clinically acceptable misfit values. Absolute passive fit was not achieved.